[moderation] [mm?] general protection fault in ksm_scan_thread

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 01af33cc9894 Add linux-next specific files for 20240125
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=12ef0487e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b73726a6eef71f1
dashboard link: https://syzkaller.appspot.com/bug?extid=c00ebf22d66d5a066087
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
CC: [ak...@linux-foundation.org linux-...@vger.kernel.org linu...@kvack.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bd3f86d4b4a5/disk-01af33cc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/39432e805e81/vmlinux-01af33cc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ebd665cc1f02/bzImage-01af33cc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c00ebf...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000084: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000420-0x0000000000000427]
CPU: 0 PID: 35 Comm: ksmd Not tainted 6.8.0-rc1-next-20240125-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:scan_get_next_rmap_item mm/ksm.c:2641 [inline]
RIP: 0010:ksm_do_scan mm/ksm.c:2754 [inline]
RIP: 0010:ksm_scan_thread+0x35b/0x5110 mm/ksm.c:2780
Code: ff ff ff ff e8 66 50 c3 08 48 85 c0 48 89 04 24 0f 84 4e 13 00 00 e8 64 31 a6 ff 48 8b 04 24 48 8d 78 20 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 0f 85 f2 3c 00 00 4c 8b 34 24 31 ff 49 8b 5e 20 81
RSP: 0018:ffffc90000ab7ce8 EFLAGS: 00010207
RAX: 0000000000000084 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: ffff88801be85a00 RSI: ffffffff81e60e0c RDI: 0000000000000426
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000001
R13: dffffc0000000000 R14: ffff88804c621550 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555574ac750 CR3: 0000000023858000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:242
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:scan_get_next_rmap_item mm/ksm.c:2641 [inline]
RIP: 0010:ksm_do_scan mm/ksm.c:2754 [inline]
RIP: 0010:ksm_scan_thread+0x35b/0x5110 mm/ksm.c:2780
Code: ff ff ff ff e8 66 50 c3 08 48 85 c0 48 89 04 24 0f 84 4e 13 00 00 e8 64 31 a6 ff 48 8b 04 24 48 8d 78 20 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00 0f 85 f2 3c 00 00 4c 8b 34 24 31 ff 49 8b 5e 20 81
RSP: 0018:ffffc90000ab7ce8 EFLAGS: 00010207
RAX: 0000000000000084 RBX: 0000000000000000 RCX: dffffc0000000000
RDX: ffff88801be85a00 RSI: ffffffff81e60e0c RDI: 0000000000000426
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000001
R13: dffffc0000000000 R14: ffff88804c621550 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2bc2c000 CR3: 000000007ec3a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 4 bytes skipped:
0: e8 66 50 c3 08 call 0x8c3506b
5: 48 85 c0 test %rax,%rax
8: 48 89 04 24 mov %rax,(%rsp)
c: 0f 84 4e 13 00 00 je 0x1360
12: e8 64 31 a6 ff call 0xffa6317b
17: 48 8b 04 24 mov (%rsp),%rax
1b: 48 8d 78 20 lea 0x20(%rax),%rdi
1f: 48 89 f8 mov %rdi,%rax
22: 48 c1 e8 03 shr $0x3,%rax
* 26: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1) <-- trapping instruction
2b: 0f 85 f2 3c 00 00 jne 0x3d23
31: 4c 8b 34 24 mov (%rsp),%r14
35: 31 ff xor %edi,%edi
37: 49 8b 5e 20 mov 0x20(%r14),%rbx
3b: 81 .byte 0x81


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.